1. Field of the Invention
This invention relates to a function-separated type electrophotographic photosensitive member for infrared rays, which is comprised of a combination of an organic photoconductor serving as a charge generation material, with a charge transport material.
2. Related Background Art
Pigments and dyes exhibiting photoconductivity have been hitherto reported in a great number of publications. For example, RCA review Vol. 23, pp. 413-419 September 1962) reports photoconductivity of phthalocyanine pigments, and U.S. Pat. Nos. 3,397,086 and 3,816,118 disclose electrophotgraphic photosensitive members employing such phthalocyanine pigments. Other organic photoconductive materials used for electrophotographic photosensitive members may include, for example, pyrilium type dyes disclosed in U.S. Pat. Nos. 4,315,983 and 4,327,169 or Research Disclosure 20517 (May, 1981), squaric acid methine dyes disclosed in U.S. Pat. No. 3,824,099, and disazo pigments disclosed in U.S. Pat. Nos. 3,898,084 and 4,251,613.
These organic photoconductive materials can be synthesized more easily as compared with inorganic photoconductive materials. Moreover, the color sensitivity thereof can be controlled since they can be relatively easily changed to have a different photosensitive wavelength region in respect of the sensitivity to visible light by changing molecular arrangement. They are also free from environmental pollution, and have remarkably superior productivity and economical advantages as compared with inorganic photoconductive materials. For these reasons, manufacturers are recently competing with each other to speed development, and there have been available not a few photoconductive materials that have attained practically utilizable levels in respect of sensitivity, durability and so forth.
On the other hand, recent years, there is a rapidly increasing demand that these organic photoconductive materials might be desirably used for photosensitive members for digital recording means such as a laser printer by extending the photosensitive wavelength region up to the infrared wavelength, in particular, the wavelength for a semiconductor laser (at the present state of the art, most preferably 750 mm or more, particularly around 780 to 800 nm from practical viewpoints such as economical advantage, output, matching with photosensitive materials, etc.). Considering the conventional organic photoconductive materials from these points of view, the above-mentioned phthalocyanine pigments, aluminum phthalocyanine pigments disclosed in U.S. Pat. No. 4,426,434 which are improvements of the phthalocyanine pigments, triphenylamine type trisazo pigments disclosed in U.S. Pat. Nos. 4,436,800 and 4,439,506, tetrakisazo pigments disclosed in U.S. Pat. No. 4,447,513, etc. are proposed as organic photoconductive materials for near infrared rays.
However, particularly when the organic photoconductive materials are used as photosensitive members for semiconductor lasers, it is required firstly that they have a photosensitive wavelength region extending up to a long wavelength, secondly that they have good sensitivity and durability, that they have constant sensitivity over a wide wavelength region as the wavelength of the semiconductor may vary depending on temperature when used, and further that they have good productivity. The organic photoconductive materials mentioned above do not suffficiently satisfy these conditions.
As a result of intensive repeated studies, the present inventors have succeeded in providing a novel organic photoconductive material that can perfectly satisfy the above conditions.